1. Field of the Invention
This invention relates to a magnetic tape drive, and more particularly a magnetic tape drive in which a magnetic tape having information written by a 18-track magnetic tape drive is read by a magnetic tape drive for 36-track magnetic tape.
2. Description of the Prior Art
In the case that a magnetic tape having information written by an 18-track magnetic tape drive is read by a 36-track magnetic tape drive in the prior art system of a magnetic tape drive for writing or reading information into or out of a magnetic tape with a width of 1/2 inch, only 18 forward reading heads of the magnetic heads for 36 tracks installed in the device were used.
However, the aforesaid prior art magnetic tape drive had some disadvantages as follows. That is, as shown in FIG. 3, there occurs sometimes that a writing position of data, i.e. a position of a track 11 in a magnetic tape written by the 18-track magnetic tape drive is displaced from its normal position due to a certain reason, a so-called tracking displacement is produced. In addition, there occurs sometimes that a position of each of the magnetic heads of the 36-track magnetic tape drive for reading information, i.e. positions of a forward reading head 2 and a reverse reading head 3 may produce a tracking displacement due to a mechanical cause. In these cases, they produced an inconvenience that a reading output value of the 36-track magnetic tape drive becomes low as compared with that of normal case due to the fact that the writing position for data of the magnetic tape and the reading position for the data of the magnetic head are displaced from each other.
In particular, in the magnetic tape drive where a writing/reading for a track with a high writing density is required, a width of each of the tracks is narrow and a space between each of the adjoining tracks becomes narrow. Further, since the space between each of the magnetic heads was also narrow, it generated a disadvantage that it was difficult to restrict a mechanical tracking displacement.